Technology billionaire Sean Parker is putting his money where his mouth is when it comes to pot legalization. The former FacebookFB -0.61% president donated $500,000 to back a proposed initiative to legalize recreational marijuana use for adults in California, according to state campaign finance records filed Thursday.

“I’ve been following this issue with great interest for some time,” Parker told Forbes in November, when he first announced his intent to support the campaign. “It’s very encouraging to see a vibrant community of activists, many of whom have dedicated their lives to this issue, coming together around a sensible reform based measure that protects children, gives law enforcement additional resources, and establishes a strong regulatory framework for responsible adult use of marijuana–one that will yield economic benefits for all Californians.”

Under the measure, it would be legal for adults 21 years or older to possess, use and buy up to one ounce of marijuana. The law would also impose a 15% sales tax and additional state cultivation taxes. Legislative analysts predict it would bring in more than $1 billion in state and local tax revenues.